I had a GF3 before the GF5 I have now. The GF3 screen was not as nice as the GF5's, but I could use it to frame my shots which is really all a screen of that size is good for anyway. The GX1's better sensor will give you a better result in the files that come out of the camera.

So you give up a little on the screen, but you gain a better sensor, a hotshoe, and several other useful features. The GX1 also has the option of an external EVF if you want an alternative to the LCD.